This invention relates generally to metalization systems and more particularly to metalization systems for semiconductor integrated circuits.
As is known in the art, metalization systems in modern integrated circuits typically include multi-level patterns of electrical conductors, or leads separated by a dielectric, typically silicon dioxide. One significant problem which is evolving is the conductance of heat generated in a lead at an upper level to the substrate, typically silicon. The leads in various levels are electrically interconnected by conductive vias which pass through the dielectric between the leads which are to be electrically interconnected. While these conductive vias also provide for the transfer of heat in an upper lead to a lower lead, which heat is then transferred to the more thermally conductive substrate, in some region of the integrated circuit, there are leads which are less proximate to a via. This situation becomes even more significant with low dielectric constant films, such as spin-on glasses, organic polymers or xerogels as the inter-metalization layer dielectric material since their thermal conductivities are at least an order of magnitude smaller than that of plasma enhanced chemical vapor deposition (PECVD) silicon dioxide. For example, plasma enhanced tetraethyl oxosilane (PETEOS) oxide has a thermal conductivities of around 1 W/m.degree.K. Dielectrics such as spin-on-glass, organic polymers and xerogels, have reduced dielectric constants, e.g., less than 3, but their thermal conductivities will also be about an order of magnitude smaller. Thus, while it is desirable to use dielectric materials having low dielectric constants to provide lower capacitance between overlaying metal leads, these lower dielectric constant materials have lower thermal conductivity thereby reducing their effectiveness in conducting heat from a lead which is less proximate to a conductive via to the substrate.